Do you have two user accounts? You appear to be suggesting edits from an account that differs from the account that you originally posted your question from. If you contact the moderators, then they can merge the two accounts for you.
– GreenonlineJun 3 '17 at 10:06

I have rejected the edit as it changes the focus of the question. What you asked in your edit was a good question - I highly suggest that you ask it as another question (if it hasn't been asked already).
– sa_leinadJun 5 '17 at 4:05

2 Answers
2

can you show us where this is explained? The boot loader is just a program and so is the sketch. I do not see why a sketch can not do what the OP asked. That said, the knowledge to read the SDCard and modify the non-volatile program memory goes way beyond common Arduino programming knowledge. One would have to be very familiar the the particular micro processor being used. Even then it would be a challenge. To put it another way, this task is easily on par with that of creating the Arduino boot loader in the first place.
– st2000Jun 1 '17 at 11:52

@st2000 the bootloader has this extra privilege that a regular sketch hasn't.
– GerbenJun 1 '17 at 14:54